A novel direct drive linear tube generator for ocean wave energy conversion

<p>This thesis focuses on the development of a novel speed amplified power take-off system of wave energy converters that take advantage of the hydrodynamic forces from ocean surface heave movement to convert the wave kinetic energy to electrical energy.</p> <p>Ocean wave energy conversion is facing many obstacles such as the low frequencies, long periods of ocean waves, the complexity of the hydrodynamics and fluidsolid interactions, and the effective design for the PTO (Power Take-Off) mechanisms. Over the past decades, several concepts of wave energy converters (WECs) have been proposed and developed. Nevertheless, the PTO designs of point absorbers are focused on the single-speed system which requires a complicated structure to fix the PTO on the ocean bottom. In order to increase the relative speed of the translator with respect to the stator, a novel concept design of the PTO is proposed where the PTO is placed inside the buoy.</p> <p>On the other hand, the output power is not accurately predicted for the WEC because most studies treat the PTO as a dashpot of damping. In this study, the PTO damping is separated into electrical damping and mechanical damping for study. A comprehensive linear system mathematical model was formulated and simulated in both the frequency and time domains. The simulation results in the frequency domain have been verified by those in the time domain, which has validated the linear system mathematical model. The harvested electrical power could be predicted according to the connected circuit.</p> <p>The output power of PTO has been optimized using the Taguchi method, machine learning response surface methodology (RSM) and deep learning artificial neural network (ANN) method. The cogging force of the linear generator of PTO has also been minimized using the semi-closed stator and phase-shifting windings. The prediction models were validated and utilized to optimize the novel speed amplified WEC for the maximum power output under different wave conditions. Finally, the prototype of the novel speed amplified mechanism was built and validated by lab testing.</p>